1. Field of the Invention
The present invention relates to a reversible thermosensitive recording medium. Preferably, the invention recording medium is capable of recording and erasing images repeatedly by reversibly changing between a transparent state and an opaque state by changing the temperature of the recording medium. This invention also relates to a method for producing the medium.
2. Discussion of the Art
A variety of information recording media have been developed to comply with the demands for expanding and diversifying the volume of the information recorded and yet conserving resources and reducing environmental problems. Reversible thermosensitive recording media have been attracting much attention recently over other recording media, due to advantages such as the reversible temporary recording of image information and erasing the information on demand at relatively low cost without complicated developing steps.
As conventional examples of reversible thermosensitive recording media, there is known a recording medium in which a low-molecular-weight organic material such as a higher fatty acid is dispersed in a matrix resin such as vinylchloride-vinylacetate copolymer with a relatively low glass transition temperature, ranging from approximately 50.degree. C. to less than 80.degree. C. (Japanese Laid-Open Patent Applications 54-119377 and 55-154198).
There is also known a reversible thermosensitive recording medium containing a low-molecular-weight organic material with its concentration increased in the direction of the thickness towards a supporting substrate of the medium (Japanese Laid-Open Patent Application H5-8538).
In order to extend the temperature range of the transparent state, a reversible thermosensitive recording medium is disclosed, having a periodic structure of the particles of a low-molecular-weight organic material, which are dispersed in the form of discrete domains in the matrix resin and constituting a phase separation structure with a periodic distance of 1.5 microns or more in Japanese Laid-Open Patent Application H6-72032.
However, display quality in its opaque state and durability of high quality image formation for repeated cycles of the reversible thermosensitive recording media were still insufficient from practical point of view.